This invention relates to packaging electrical components.
One approach to packaging electrical components (FIG. 1) includes a housing which both encloses the components and aids in the removal of heat from power dissipating components within the housing. The housing includes a non-conductive casing 5 and an aluminum heat-sinking base 6. A printed circuit board (PCB) 3 is mounted next to the upper wall 5a of the casing. Conductive pins 7 are attached directly to the PCB 3 and extend up through wall 5a. Electronic components 9a, 9c are mounted to one or both sides of the PCB 3 (upper side 3a and lower side 3b). Larger components such as inductor 9c are mounted to the lower side 3b for space reasons. Power-dissipating components 9b are mounted directly to the baseplate 6 for better heat transfer. Component 9b is electrically connected to the PCB by leads 12.
The pins 7 allow assembly 1 to be mounted to a circuit board 14; the baseplate 6 provides a flat, thermally conductive surface from which heat generated within the assembly may be removed by free or forced convection or by mounting a heat sink (not shown) to the surface of the baseplate.
Assembly 1 is filled with an epoxy encapsulant which becomes relatively rigid upon curing. The encapsulant acts as a thermal spreader and provides mechanical support. To assure that the case and base are held together tightly, a pocket 6a is formed in the baseplate with undercuts 6b formed along the edge of the pocket. The encapsulant extends into the undercuts and has enough tensile strength to minimize the chances of the case being pulled away from the base. To protect the components from damage by shrinkage of the stiff encapsulant which may occur during curing or exposure to low temperatures, sensitive components (e.g., glass diodes, ceramic resistors or capacitors, magnetic cores) are covered with a "buffer coating" of a soft, rubbery material.